Conventionally, a pressure-sensitive adhesive film has been used for bonding a first substrate, for example, a display panel such as plasma display panel, to a second substrate, for example, a chassis for disposing a display. At present, it is demanded that after a product comprising bonded substrates is used for a long time, the pressure-sensitive adhesive film is easily and clearly removed to separate the parts constituting each substrate. For example, a display panel and a chassis are separated by the following methods.
(1) The display panel and the chassis are detached by applying a physical external load, for example, by reducing the cohesive force of the pressure-sensitive adhesive under heating at around 200° C. or with use of an organic solvent and giving a twist.
(2) The display panel and the chassis are separated by inserting a wire, a thread or the like therebetween and cutting the pressure-sensitive adhesive film.
(3) The display panel and the chassis are separated by disposing pressure-sensitive adhesive pieces in the form of a long strip and withdrawing these from the side surface.
(4) Japanese Unexamined Patent Publication (Kokai) No. 2004-69766 and Japanese Patent Publication (Kokai) No. 2004-309551 disclose a display device where a display panel and a support plate are supported by a pressure-sensitive adhesive tape disposed therebetween and the pressure-sensitive adhesive tape can be pulled at its end part and thereby detached from the support plate.
In the case of the method (1), not a small load is imposed on the display panel and the chassis and this may cause breakage of the display or deformation of the chassis at the detachment. Also, there is a temporal restriction that the detaching operation must be performed within a time where reduction in the cohesive force due to heat or an organic solvent is effective. In the case of the method (2), when the adhesive has a high cohesive force and the resisting power is large, the pressure-sensitive adhesive film cannot be sometimes cut. In the methods (3) and (4), the film itself may be cut in the middle during the operation of removing the pressure-sensitive adhesive film, failing in successfully withdrawing the pressure-sensitive adhesive film. Furthermore, these methods have a problem such as failure in obtaining a stable effect due to change in the adhesive force with the lapse of time. In this way, on trying to detach a first substrate and a second substrate bonded together, when these substrates are a rigid substrate, the detachment is very difficult.
On the other hand, a pressure-sensitive adhesive film or sheet having also an ability of dissipating heat in an electronic device is known. Japanese Unexamined Patent Publication (Kokai) No. 2002-294192 discloses a thermally conducting flame-retardant pressure-sensitive adhesive comprising aluminum hydroxide as the flame retardant and aluminum oxide as the thermally conducting filler. However, how to detach the pressure-sensitive adhesive sheet after using such an adhesive as the thermally conducting pressure-sensitive adhesive sheet is not disclosed.